Robert Burns' diamond point engravings

Robert Burns came to know James Cunninghamme, Earl of Glencairn in Edinburgh in 1786 through a 'Letter of Introduction' provided by Dalrymple of Orangefield who was married to Lady Glencairn's sister. The Earl received the poet warmly in his house and introduced him to his friends. One of several gifts from the earl to the poet was a diamond point pen, stylus, or cutter which he used to write upon many windowpanes and glasses, scribing verse, his signature, epigrams, or other writings for posterity. Many of these diamond-point engravings survive, some however are contentious as regards either their authenticity, meaning, or both.
Burns' diamond point pen
The pen may well survive to this day, made of a cylindrical piece of wood (elder?), and has the diamond inserted at one end in a metal extension. It is held in the collection of the Rozelle House Galleries in South Ayrshire. It's Accession Number is AYRTOS:100346, The Digital Number is SABN001n. The original catalogue...